The Purest Manzanita

A day or two before New Year’s Cynthia and I went hiking up to the Gaviota Wind Caves, and then wandered on further up the trail where we found a manzanita. My first guess was that it was Arctostaphylos purissima, because:

It looked like A. refugioensis, but was too small

It was only at 200m and A. refugioensis doesn’t go that low.

These are not good reasons, and I knew I needed to revisit the plant. With a key.

Today I went back. I also revisited the trails on the other side of the Gaviota Gap (US 101) where I do believe A. refugioensis grows. I wanted to make sure I could really tell the differences and wasn’t just fooling myself into believing the key.

I visited two patches on the east of 101, and found four patches to the west.

Jepson’s key says that to distinguish between A. purissima and A. refugioensis one must look at the nascent inflorescences and see if they have glandular hairs or not.

Um.

We are well past the time for finding nascent inflorescences… We’re seeing nascent seeds now. Even when I looked back in December I only noticed full blooms… And I’m not sure I can tell whether a hair has a gland or not. Past attempts have not been successful…

Oh well, if I’m just looking at these two species, and not trying to key things out from scratch then these facts might be helpful:

A. purissima

A. refugioensis

height

1-4m

2-4m

leaf width

1-2cm

2-3cm

inflorescence

raceme
0-2 branched

panicle
5-10 branched

fruit size

5-8mm

10-15mm

elevation

<300m

300-820m

As for the height: Minimum sizes don’t seem very useful. I found plants no taller than 60cm in full bloom, and both species have the same maximum height. So ignore that.

Plants at both patches east of 101 had leaves that were more than 2cm wide, plants west had narrower leaves.

Arctostaphylos refugioensis leaf 2.7cm wide

As for the inflorescences, those east of 101 are much more branched than those west.

East

West

A. refugioensis multiply branched inflorescence

A. refugioensis inflorescence

A. purissima inflorescence, single raceme

Fruits are not currently ripe so their size couldn’t be tested today, but a couple of years ago I determined that the plants (I looked at) to the east of 101 had seeds bigger than 10mm.

As for elevation: one patch to the east is at ~500m, the other at about 300m, while all patches to the west were below 300m.

In other words east of the Gaviota Gap I find A. refugioensis, and west I find A. purissima.Distribution map of Arctostaphylos around Gaviota. Blue crosses mark A. purissima, and red crosses mark A. refugioensis. (I think)

Which makes me wonder if Gaviota gap is really a divide for both species.

I don’t have enough data yet…

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